1. Field of the Invention
The present invention relates generally to laser cutting devices and, more particularly to a laser cutting device with high precision.
2. Discussion of the Related Art
Conventional methods for cutting glass sheets are based on the use of a diamond cutter or a small rotary cutter to first produce a scribed line in the glass sheet, and then break the glass sheet by application of an external mechanical force along the scribed line. The disadvantage of those methods is that the scribed line may cause fragments to be created from the surface, which can deposit on the glass and scratch it. In addition, chips can be created in the cut edge resulting in an uneven glass edge. Furthermore, micro-cracks produced on the cut edge during the scribing process lead to reduced mechanical stressability, increasing the risk of breakage. An approach for preventing the formation of fragments as well as chips and micro-cracks is to cut glass sheets using thermally induced mechanical tension. In this approach, a laser beam is directed at the glass and moved at a predetermined speed relative to the glass sheet, thereby producing such a high thermal tension that cracks form in the glass sheet. Then, the glass sheet is split into pieces mechanically.
Referring to FIG. 5, a typical laser cutting device 10 used for cutting a glass sheet 20 includes a laser source 11, a focusing lens 12, and a sprayer 13. The laser source 11 faces the focusing lens 12, and the sprayer 13 is fixed to the focusing lens 12. A laser beam emitting from the laser source 11 is focused by the focusing lens 12, and subsequently form an elliptic beam spot 111 on the glass sheet 20. In the process of cutting the glass sheet 20, the glass sheet 20 moves along the X-axis, thus keeping the major axis b of the elliptic beam spot 111 and a predetermined cutting line L1 aligned. Therefore, thermal energy of the elliptic beam spot 111 is symmetrically distributed along the predetermined cutting line L1. Then, the sprayer 13 ejects a coolant 131 onto the glass sheet 20 to cool the area heated by the elliptic beam spot 111, creating a crack 201 in the glass sheet 20 along the predetermined cutting line L1. The glass sheet 20 is split along the crack 201 by application of an external mechanical force on the glass sheet 20.
However, because the laser cutting device 10 is generally fixed to a machine tool (not shown), and the sprayer 13 is fixed to the focusing lens 12, if a predetermined cutting line L2 is curved, as shown in FIG. 6, the coolant 131 ejected by the sprayer 13 may deviate from the predetermined cutting line L2 since the coolant 131 is always aligned along the major axis b of the elliptic beam spot 111. Therefore, all portions along the predetermined cutting line L2 may not be equally cooled, leading to a reduction in cutting precision of the laser cutting device 10. Additionally, since the laser cutting device 10 is fixed to the machine tool, the major axis b of the elliptic beam spot 111 cannot be substantially aligned along a tangent T of the predetermined cutting line L2, thus leading to asymmetrical distribution of the thermal energy of the elliptic beam spot 111, and a further reduction in cutting precision.
Therefore, a laser cutting device to solve the aforementioned problems is desired.